Novel HVDC Power Transmission Architectures for Subsea Grid

Subsea electrification is envisaged as one of the key building blocks of deep-water oil and gas (O&G) production. Present power transmission and distribution (T&D) schemes almost exclusively employ high voltage AC (HVAC) technology to drive the electrical processing units in the seabed, such as pump and compressor motors. Although HVAC transmission is reliable and simple to control, it exhibits a serious drawback with increasing step-out distance in terms of high reactive power requirements and reduction in peak power transfer capability for the subsea transmission cable. Moreover, most of the existing subsea T&D architectures employ a hub-and-spoke architecture with a single power receiving node. As a result, these systems are vulnerable to single-point failure. In order to address the above issues, two novel subsea architectures, based on high voltage DC (HVDC) transmission, are proposed in this paper. HVDC offers a significant advantage over HVAC systems for longer transmission distances with additional power processing units embedded in the system. Both these architectures employ a subsea DC distribution bus concept to supply multiple subsea loads which represent current scenario of increasing subsea consumers. The performance of the proposed architectures is illustrated through simulation for distinct events such as rated power flow, load step-up/down and load side breaker closing. Relevant results are discussed to summarize the advantages and challenges for the proposed power transmission architectures.